Methods and apparatuses for monitoring and controlling mechanical or chemical-mechanical planarization of microelectronic substrate assemblies

ABSTRACT

Methods and devices for mechanical and/or chemical-mechanical planarization of semiconductor wafers, field emission displays and other microelectronic substrate assemblies. One method of planarizing a microelectronic substrate assembly in accordance with the invention includes pressing a substrate assembly against a planarizing surface of a polishing pad at a pad/substrate interface defined by a surface area of the substrate assembly contacting the planarizing surface. The method continues by moving the substrate assembly and/or the polishing pad with respect to the other to rub at least one of the substrate assembly and the planarizing surface against the other at a relative velocity. As the substrate assembly and polishing pad rub against each other, a parameter indicative of drag force between the substrate assembly and the polishing pad is measured or sensed at periodic intervals. The drag force parameter, for example, can be lateral displacement or lateral forces between a first component coupled to one of the substrate assembly or the polishing pad and a second component in either a carrier assembly holding the substrate assembly or a table supporting the polishing pad. The drag force parameter can be measured along a lateral axis to produce a waveform having minimum and maximum peaks relative to minimum and maximum peak drag forces between the substrate assembly and the polishing pad along the axis. The maximum peak drag forces or the difference of the minimum and maximum peak drag forces are processed to generate a force-time relationship. The status of a parameter, such as the onset of planarity or the endpoint of the process, is then estimated by analyzing the force-time relationship.

TECHNICAL FIELD

[0001] The present invention relates to methods and apparatuses formonitoring and controlling mechanical and/or chemical-mechanicalplanarization of semiconductor wafers, field emission displays and othertypes of microelectronic substrate assemblies.

BACKGROUND OF THE INVENTION

[0002] Mechanical and chemical-mechanical planarizing processes(collectively “CMP”) are used in the manufacturing of electronic devicesfor forming a flat surface on semiconductor wafers, field emissiondisplays and many other microelectronic substrate assemblies. CMPprocesses generally remove material from a substrate assembly to createa highly planar surface at a precise elevation in the layers of materialon the substrate assembly.

[0003]FIG. 1 is a schematic isometric view of a web-format planarizingmachine 10 for planarizing a microelectronic substrate assembly 12. Theplanarizing machine 10 has a table 11 with a rigid panel or plate toprovide a flat, solid support surface 13 for supporting a portion of aweb-format planarizing pad 40 in a planarizing zone “A.” The planarizingmachine 10 also has a pad advancing mechanism including a plurality ofrollers to guide, position, and hold the web-format pad 40 over thesupport surface 13. The pad advancing mechanism generally includes asupply roller 20, first and second idler rollers 21 a and 21 b, firstand second guide rollers 22 a and 22 b, and a take-up roller 23. Asexplained below, a motor (not shown) drives the take-up roller 23 toadvance the pad 40 across the support surface 13 along a pad travel pathT-T. The motor can also drive the supply roller 20. The first idlerroller 21 a and the first guide roller 22 a press an operative portionof the pad against the support surface 13 to hold the pad 40 stationaryduring operation.

[0004] The planarizing machine 10 also has a carrier assembly 30 totranslate the substrate assembly 12 across the pad 40. In oneembodiment, the carrier assembly 30 has a head 32 to pick up, hold andrelease the substrate assembly 12 at appropriate stages of theplanarizing process. The carrier assembly 30 also has a support gantry34 and a drive assembly 35 that can move along the gantry 34. The driveassembly 35 has an actuator 36, a drive shaft 37 coupled to the actuator36, and an arm 38 projecting from the drive shaft 37. The arm 38 carriesthe head 32 via another shaft 39. The actuator 36 orbits the head 32about an axis B-B to move the substrate assembly 12 across the pad 40.

[0005] The polishing pad 40 may be a non-abrasive polymeric pad (e.g.,polyurethane), or it may be a fixed-abrasive polishing pad in whichabrasive particles are fixedly dispersed in a resin or another type ofsuspension medium. A planarizing fluid 50 flows from a plurality ofnozzles 49 during planarization of the substrate assembly 12. Theplanarizing fluid 50 may be a conventional CMP slurry with abrasiveparticles and chemicals that etch and/or oxidize the surface of thesubstrate assembly 12, or the planarizing fluid 50 may be a “clean”non-abrasive planarizing solution without abrasive particles. In mostCMP applications, abrasive slurries with abrasive particles are used onnon-abrasive polishing pads, and non-abrasive clean solutions withoutabrasive particles are used on fixed-abrasive polishing pads.

[0006] In the operation of the planarizing machine 10, the pad 40 movesacross the support surface 13 along the pad travel path T-T eitherduring or between planarizing cycles to change the particular activeportion of the polishing pad 40 in the planarizing zone A. For example,the supply and take-up rollers 20 and 23 can drive the polishing pad 40between planarizing cycles such that a point P moves incrementallyacross the support surface 13 to a number of intermediate locations I₁,I₂, etc. Alternatively, the rollers 20 and 23 may drive the polishingpad 40 between planarizing cycles such that the point P moves all theway across the support surface 13 to completely remove a used portion ofthe pad 40 from the planarizing zone A. The rollers may alsocontinuously drive the polishing pad 40 at a slow rate during aplanarizing cycle such that the point P moves continuously across thesupport surface 13. Thus, the polishing pad 40 should be free to moveaxially over the length of the support surface 13 along the pad travelpath T-T.

[0007] CMP processes should consistently and accurately produce auniform, planar surface on substrate assemblies to enable circuit anddevice patterns to be formed with photolithography techniques. As thedensity of integrated circuits increases, it is often necessary toaccurately focus the critical dimensions of the photo-patterns to withina tolerance of approximately 0.1 μm. Focusing photo-patterns to suchsmall tolerances, however, is difficult when the planarized surfaces ofsubstrate assemblies are not uniformly planar. Thus, to be effective,CMP processes should create highly uniform, planar surfaces on substrateassemblies.

[0008] In the highly competitive semiconductor industry, it is alsodesirable to maximize the throughput of CMP processing by producing aplanar surface on a substrate assembly as quickly as possible. Thethroughput of CMP processing is a function of several factors; one ofwhich is the ability to accurately stop CMP processing at a desiredendpoint. In a typical CMP process, the desired endpoint is reached whenthe surface of the substrate assembly is planar and/or when enoughmaterial has been removed from the substrate assembly to form discretecomponents (e.g., shallow trench isolation areas, contacts, damascenelines). Accurately stopping CMP processing at a desired endpoint isimportant for maintaining a high throughput because the substrateassembly may need to be re-polished if it is “under-planarized,” or toomuch material can be removed from the substrate assembly if it is“over-polished.” For example, over-polishing can completely destroy asection of the substrate assembly or cause “dishing” inshallow-trench-isolation structures. Thus, it is highly desirable tostop CMP processing at the desired endpoint.

[0009] One method for determining the endpoint of CMP processing isdescribed in U.S. Pat. No. 5,036,015 issued to Sandhu (“Sandhu”), whichis herein incorporated by reference. Sandhu discloses detecting theplanar endpoint by sensing a change in friction between a wafer and thepolishing medium. Such a change of friction may be produced by adifferent coefficient of friction at the wafer surface as one material(e.g. an oxide) is removed from the wafer to expose another material(e.g., a nitride). In addition to the different coefficients of frictioncaused by a change of material at the substrate surface, the frictionbetween the wafer and the planarizing medium can change during CMPprocessing because the surface area of the substrate contacting thepolishing pad changes as the substrate becomes more planar. Sandhudiscloses endpointing CMP processing by measuring the current drawthrough a drive motor to estimate the friction between the substrateassembly and the polishing pad, and then detecting a change in the motorcurrent to estimate planarity or an interface between materials.

[0010] Although Sandhu discloses a viable process for endpointing CMPprocessing, the change in current draw through a drive motor may notaccurately indicate the endpoint of a substrate assembly. For example,because the friction between the substrate assembly and the planarizingmedium can increase or decrease throughout a planarizing cycle accordingto both topography of the substrate assembly and the materials, it maybe difficult to identify a definite change in the motor currentindicating that the endpoint has been reached. Moreover, otherparameters that are not related to the drag force between the pad andthe substrate assembly, such as function losses and other power lossesin the motors, gearboxes or other components, may change the currentdraw through the motors independently from the drag force or have asignificantly greater magnitude than the drag force. The change incurrent through the drive motors, therefore, may not accurately reflectthe drag force between the wafer and the polishing pad because the dragforce is not the only factor or even the primary factor that influencesthe current draw. Thus, it would be desirable to develop an apparatusand method for more accurately endpointing planarization ofmicroelectronic substrate assemblies.

SUMMARY OF THE INVENTION

[0011] The present invention is directed toward mechanical and/orchemical-mechanical planarization of semiconductor wafers, fieldemission displays and other microelectronic substrate assemblies. Onemethod of planarizing a microelectronic substrate assembly in accordancewith the invention includes pressing a substrate assembly against aplanarizing surface of a polishing pad at a pad/substrate interfacedefined by a surface area of the substrate assembly contacting theplanarizing surface. The method continues by moving the substrateassembly and/or the polishing pad with respect to the other to rub atleast one of the substrate assembly and the planarizing surface againstthe other at a relative velocity. As the substrate assembly andpolishing pad rub against each other, a parameter indicative of dragforce between the substrate assembly and the polishing pad is measuredor sensed at periodic intervals. The drag force parameter, for example,can be lateral displacement or lateral forces between a first componentcoupled to one of the substrate assembly or the polishing pad and asecond component in either a carrier assembly holding the substrateassembly or a table supporting the polishing pad. The drag forceparameter can be measured along a lateral axis to produce a waveformhaving minimum and maximum peaks relative to minimum and maximum peakdrag forces between the substrate assembly and the polishing pad alongthe lateral axis. The maximum peak drag forces, or the differencesbetween the maximum and minimum peak drag forces, are processed togenerate a force-time relationship. The status of a parameter, such asthe onset of planarity or the endpoint of the process, is then estimatedby analyzing the force-time relationship.

[0012] In one particular embodiment of a method in accordance with theinvention, the substrate assembly comprises a shallow-trench-isolationstructure including a substrate having trenches, an endpoint layer overthe substrate, and a cover layer over the endpoint layer that fills thetrenches. The procedure of estimating the status of a parameter of theplanarizing process comprises assessing an endpoint at the endpointlayer. In this particular embodiment, the endpoint is assessed byperforming a first regression on a downward slope in the force-timerelationship to determine a first line, performing a second regressionon a relatively flat slope in the force-time relationship to determine asecond line, and assessing an exposure time at an intersection of thefirst and second lines. The exposure time provides an estimation of whenportions of the endpoint layer at the desired endpoint elevation areexposed to the polishing pad. Several embodiments of methods inaccordance with the invention further include terminating removal ofmaterial from the substrate assembly at an endpoint time equal to theexposure time plus a predetermined over-polish time.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is an isometric view of a web-format planarizing machine inaccordance with the prior art.

[0014]FIG. 2 is a schematic cross-sectional view of a web-formatplanarizing machine having a monitoring system in accordance with anembodiment of the invention.

[0015]FIG. 3 is a flowchart of an illustrative method in accordance withone embodiment of the invention.

[0016]FIG. 4 is a schematic cross-sectional view of a substrate assemblybeing planarized with a method in accordance with an embodiment of theinvention.

[0017]FIG. 5 is a graph of a waveform of the drag forces at thepad/substrate interface along a lateral axis versus time in accordancewith an embodiment of the invention.

[0018]FIG. 6 is a graph of the peak drag forces at the pad/substrateinterface versus time.

[0019]FIG. 7 is a schematic isometric view of a web-format planarizingmachine having a cut-away portion illustrating an endpointing apparatusin accordance with an embodiment of the invention.

[0020]FIG. 8 is a schematic cross-sectional view of the planarizingmachine of FIG. 7 along line 8-8.

[0021]FIG. 9 is a schematic cross-sectional view of a planarizingmachine in accordance with another embodiment of the invention.

[0022]FIG. 10 is a schematic cross-sectional view of a planarizingmachine in accordance with still another embodiment of the invention.

[0023]FIG. 11 is a schematic isometric view of a planarizing machine inaccordance with another embodiment of the invention.

[0024]FIG. 12 is a schematic isometric view of a rotary planarizingmachine with a cut-away section illustrating an endpointing apparatus inaccordance with another embodiment of the invention.

[0025]FIG. 13 is a schematic cross-sectional view of the planarizingmachine of FIG. 12 taken along line 13-13.

[0026]FIG. 14 is a schematic cross-sectional view of a substrate holderhaving an endpointing apparatus in accordance with yet anotherembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention relates to planarizing machines and methodsfor monitoring and controlling planarizing processes in mechanical orchemical-mechanical planarization of microelectronic substrateassemblies. Many specific details of the invention are described belowwith reference to planarizing semiconductor wafers using web-format androtary planarizing machines to provide a thorough understanding of suchembodiments. For example, general aspects of a representative web-formatplanarizing machine and illustrative methods for controlling CMPprocessing using this machine are initially described below withreference to FIGS. 2-6. Several detailed embodiments of planarizingmachines for practicing methods in accordance with the invention arethen described with reference to FIGS. 7-14. The present invention,however, may have additional embodiments and/or can be practiced withoutseveral of the details described in the following description.

[0028] A. Representative Planarizing Machines and Monitoring Systems

[0029]FIG. 2 is a schematic cross-sectional view of a web-formatplanarizing machine 100 having a monitoring system for monitoring andcontrolling planarization of a microelectronic substrate assembly 12 inaccordance with the invention. The planarizing machine 100 includes atable 110, a carrier assembly 130 over the table 110, and a polishingpad 140 on the table 110. The carrier assembly 130 and the polishing pad140 can be substantially the same as those describe above with referenceto FIG. 1. The polishing pad 140 is accordingly coupled to apad-advancing mechanism having a plurality of rollers 120-123. Thepad-advancing mechanism can also be the same as that described abovewith reference to FIG. 1.

[0030] The planarizing machine 100 also includes a monitoring systemthat measures the drag force between the substrate assembly 12 and thepolishing pad 140 during planarization to endpoint or control otheraspects of the CMP process. The monitoring system can include a dragforce measuring assembly 160 (identified by reference numbers 160 a and160 b) to measure a parameter that accurately indicates the drag forcebetween the pad 140 and the substrate assembly 12 along a lateral axis.The lateral axis can extend generally parallel to a plane defined by theinterface of the pad 140 and the substrate assembly 12. The drag forcemeasuring assembly 160 generates a waveform having minimum and maximumdrag force peaks along the lateral axis. The waveform, for example, canbe a generally sinusoidal wave with varying amplitudes corresponding tothe minimum and maximum drag forces along the lateral axis.

[0031] The drag force measuring assembly 160 can be coupled to the table110 and/or a carrier head 132 of the carrier assembly 130. The dragforce measuring assembly 160 is generally configured to isolate a dragforce parameter indicative of drag forces between the substrate assembly12 and the polishing pad 140 that is not influenced by energy losses inmotors, gears or other components that drive either the polishing pad140 or the carrier head 132. For example, the drag force measuringassembly 160 a in the table 110 can have a first component 162 a coupledto the polishing pad 140, a second component 164 a that is fixedlyattached to or integral with the table 110, and a force detector 190 todetect lateral forces or lateral displacement between the firstcomponent 162 a and a second component 164 a. The drag force measuringassembly 160 b in the carrier assembly 130 can include a first component162 b coupled to the substrate assembly 12 and a second component 164 bcoupled to either the carrier head 132, the shaft 139 or anothercomponent of the carrier assembly 130. The drag force measuring assembly160 b also has a force detector 190 to detect lateral forces or lateraldisplacement between the first and second components 162 b and 164 b.The drag force parameter can accordingly be lateral displacement orlateral forces between the first component 162 (identified by referencenumbers 162 a and 162 b) and the second component 164 (identified byreference numbers 164 a and 164 b) corresponding to a shear forcebetween the substrate assembly 12 and the planarizing surface 142 of thepolishing pad 140. Several embodiments of force detectors 190 and dragforce measuring assemblies that isolate the drag force parameter frompower losses are described in detail below with reference to FIGS. 7-14.

[0032] The drag force monitoring system can also include a processor 199coupled to the drag force measuring assembly 160. The processor 199receives signals from the drag force measuring assembly 160corresponding to the waveform of the measured drag forces. The processorgenerates a force-time relationship between the peak drag forces of thewaveform and time. In one particular application of the presentinvention for planarizing a substrate assembly having ashallow-trench-isolation structure (“STI”), the force-time relationshipgenerally has an initial section with an increasing slope, anintermediate section with a decreasing slope, and a final section with arelatively flat slope. The processor 199 can further perform a firstregression on the intermediate section to generate a first line and asecond regression on the final section to generate a second line. Theprocessor determines a reference time indicating the exposure of anendpointing layer by determining the time corresponding to theintersection between the first and second lines. The processor 199 thenendpoints CMP processing of the STI substrate assembly at an estimatedendpoint time equal to approximately the reference time plus apredetermined over-polish time. Several methods for controlling orendpointing CMP processing using the force-time relationship between thepeak drag forces and time are set forth below.

[0033] B. Illustrative Methods for Endpointing and Controlling CMPProcessing

[0034]FIG. 3 is a flowchart of a method for endpointing CMP processingof the substrate assembly 12 in accordance with one embodiment of theinvention. The method illustrated in FIG. 3 is a comprehensive methodthat includes several procedures that may be combined with each other orcompletely excluded in other embodiments of the invention. Accordingly,other embodiments of the invention may also include different proceduresor a different order of procedures. The CMP process of FIG. 3 is alsoapplicable to several different types of semiconductor wafers, fieldemission displays and other microelectronic substrate assemblies.

[0035] The planarizing process illustrated in FIG. 3 includes removingmaterial from a substrate assembly by pressing the substrate assemblyagainst a planarizing surface (procedure 410) and moving the substrateassembly and/or the polishing pad with respect to the other (procedure412). The polishing pad can be the web-format pad 140 shown in FIG. 2 ora rotary pad. The polishing pad can also be a fixed-abrasive pad withabrasive particles fixedly attached to a suspension medium or anon-abrasive pad without abrasive particles. The substrate assembly isgenerally pressed against the polishing pad in the presence of aplanarizing solution.

[0036]FIG. 4 is a schematic cross-sectional view illustrating theremoval of material from an STI substrate assembly 12. The STI substrateassembly 12 has a substrate 13 with a plurality of trenches 14, anendpointing layer 15 composed of a first material with a first polishingrate, and a fill layer 16 or cover layer composed of a second materialhaving a second polishing rate different than the endpointing layer 15.The endpointing layer 15 is generally a polish-stop layer that has alower polishing rate than the cover layer 16 to inhibit planarizationbelow lands 17 at a desired endpoint elevation in the substrate assembly12. In an alternate embodiment, the endpoint layer 15 can have a higherpolishing rate than the cover layer 16. The endpointing layer 15, forexample, can be a silicon nitride or carbon polish-stop layer, and thefill layer 16 can be a doped or undoped silicon dioxide layer. Thesubstrate assembly 12 contacts the planarizing surface 142 of thepolishing pad 140 at a pad/substrate interface 143 defined by thesurface area “SA” in contact with the planarizing surface 142. Thecarrier assembly 130 presses the substrate assembly 12 against theplanarizing surface 142 at a downforce F_(d). The carrier assembly 130also moves the substrate assembly 12 with respect to the polishing pad140 to rub the substrate assembly 12 against the planarizing surface 142at a relative velocity V_(r). The friction between the substrateassembly 12 and the planarizing surface 142 creates a drag force F_(D)that acts against the polishing pad 140.

[0037] Referring again to FIG. 3, the planarizing process 400 continueswith a measuring procedure 420 that includes measuring a drag forceparameter indicative of the drag force F_(D) between the substrateassembly 12 and the polishing pad 140. The drag force parameter isgenerally isolated from energy losses in components that drive eitherthe polishing pad or the substrate assembly to provide a more accurateindication of the drag force F_(D) at the pad/substrate interface 143(FIG. 4). The drag force parameter can be measured along a lateral axisthat is generally parallel to a plane defined by the pad/substrateinterface to generate the sinusoidal waveform (examples of lateral axesare identified by lines L₁ or L₂ of FIG. 7). Several devices forisolating and measuring the drag force parameter are described belowwith reference to FIGS. 7-14.

[0038] The planarizing process continues with a data processingprocedure 430 in which a waveform of the measured drag force isgenerated. FIG. 5 is a graph of a waveform 432 of the measured dragforce F_(D) along a lateral axis at the pad/substrate interface for anSTI substrate assembly over time. The measured waveform 432 for the STIsubstrate assembly has a plurality of maximum peaks 434 (identified byreference numbers 434 a and 434 b) and a plurality of minimum peaks 436(identified by reference numbers 436 a and 436 b). The maximum andminimum peaks 434 and 436 correspond to the maximum and minimum dragforces between the pad 140 and a substrate assembly 12 along the lateralaxis. The waveform 432 is generally a sinusoidal waveform in which theamplitude between the maximum peaks 434 and the minimum peaks 436indicates increases or decreases in the drag force at the pad/substrateinterface. For an STI substrate assembly, the waveform 432 has a firstsection 437 in which the peak-to-peak amplitude increases, a secondsection 438 in which the peak-to-peak amplitude decreases, and a thirdsection 439 in which the peak-to-peak amplitude remains substantiallyconstant.

[0039] The method 400 shown in FIG. 3 further continues with acorrelating procedure 440 in which the maximum peak drag forces 434, orthe differences between the maximum and minimum peak drag forces 434 and436 (FIG. 5), are correlated with time to generate a force-timerelationship. In another embodiment, the correlating procedure 440 cancorrelate the minimum peak drag forces 436 with time The correlatingprocedure 440 produces a peak drag force curve corresponding to the peakdrag forces along the lateral axis.

[0040]FIG. 6 is a graph illustrating a peak drag force curve 442corresponding to either the maximum peak drag forces 434 or thedifferences between the maximum and minimum peak drag forces 434 and 436of the waveform 432 shown in FIG. 5. The times t₁ and t₂ in FIG. 5correspond to the times t₁ and t₂ in FIG. 6. The peak drag force curve442 has a first or initial section 447 with an increasing slopecorresponding to the increasing peak drag forces 434 in the firstsection 437 of the waveform 432 shown in FIG. 5. The peak drag forcecurve 442 has a second or intermediate section 448 with a generallydownward slope corresponding to the decreasing peak drag forces 434 ofthe waveform 432 shown in FIG. 5. The peak drag force curve 442 also hasa third or end section 449 with a relatively flat slope corresponding tothe substantially constant peak drag forces 434 in the third section 439of the waveform 432 shown in FIG. 5. The peak drag force curve 442 isused to estimate the endpoint of the planarizing cycle or to estimatethe status of another parameter of the CMP process.

[0041] The process 400 of FIG. 3 further includes an estimatingprocedure 450 for estimating a reference time t_(r) corresponding to anexposure time that the lands 17 of the endpoint layer 15 (FIG. 4) areexposed during planarization. The estimating procedure includesperforming a mathematical regression of the intermediate section 448 ofthe peak drag force curve 442 to create a downwardly sloping first line444, and performing a regression of the end section 449 of the peak dragforce curve 442 to determine a second line 446. Suitable software orhardware for performing the regressions of the peak drag force curve 442are commercially available and known to those skilled in thesemiconductor manufacturing arts. The reference time is estimated bydetermining the time corresponding to the intersection between the firstline 444 and the second line 446.

[0042] The method 400 of FIG. 3 continues with a terminating procedure460 that terminates removal of the material from the substrate assembly12 at an estimated endpoint time. The terminating procedure 460calculates the estimated endpoint time by adding a predeterminedover-polish time to the reference time t_(r). In a typical STIapplication, the over-polish time is approximately 10-50 seconds, andmore specifically approximately 25-35 seconds. The estimating procedure450 actually occurs during the initial portion of the third section 449of the peak-drag force curve 442 (FIG. 6) because a sufficient number ofdata points indicating that the planarizing process has entered the endsection 449 must be obtained. In several STI applications, the referencetime t_(r) corresponding to the exposure of the endpoint layer 15 (FIG.4) can be calculated approximately 7 seconds after the peak drag forcecurve 442 enters the third section 449. Therefore, because theover-polish time is approximately 10-50 seconds after the reference timet_(r) occurs, the terminating procedure 460 can estimate the endpoint ofthe planarizing process in situ and in real time.

[0043] C. Embodiments of Endpointing and Drag Force Measuring Assemblies

[0044] FIGS. 7-14 illustrate several embodiments of endpointingapparatuses that execute the measuring procedure 420 (FIG. 3) byisolating a drag force parameter related to the drag force between thesubstrate assembly 12 and the polishing pad 140 from other energylosses, and measuring the isolated drag force during planarization. Forthe following description, the endpointing apparatuses described inFIGS. 7-14 define one type of drag force measuring assembly 160 shown inFIG. 2. Therefore, it will be understood that the drag force measuredwith the endpointing apparatuses shown in FIGS. 7-14 can also be used todiagnose or control other aspects of the CMP processes described abovewith reference to FIGS. 2-6.

[0045]FIG. 7 is a schematic isometric view of the web-format planarizingmachine 100 including an endpointing apparatus for measuring the dragforce between the substrate assembly 12 and the polishing pad 140 duringplanarization. The endpointing apparatus generally includes a secondarysupport member defined by a sub-platen 150, a primary support memberdefined by a platen 170, and at least one force detector 190 between thesub-platen 150 and the platen 170. The platen 170 and the sub-platen 150can be separate components of the table 10. The polishing pad 140 isreleasably coupled to the platen 170 so that the drag forces FD betweenthe substrate assembly 12 and the pad 140 exert lateral forces againstthe platen 170 independent of friction losses or power losses in thecarrier assembly 130. The lateral force exerted by the pad 140 againstthe platen 170 is thus an isolated parameter indicative of the drag FDbetween the substrate assembly 12 and the pad 140.

[0046]FIG. 8 is a schematic cross-sectional view of the planarizingmachine 100 illustrating the endpointing apparatus in greater detail.Referring to FIGS. 7 and 8 together, the sub-platen 150 can be a basesupporting the platen 170. The sub-platen 150 has a recess 152 definedby a base surface 153 and a plurality of walls (identified by referencenumbers 154 a, 154 b, 156 a and 156 b) projecting upwardly from the basesurface 153 transversely with respect to a planarizing plane P-P (FIG.8). For the purposes of the present disclosure, the term “transverse”means any non-parallel arrangement and is not limited to a perpendiculararrangement. The walls can include a first side-wall 154 a, a secondside-wall 154 b opposite the first side-wall 154 a, a first end-wall 156a at one end of the side-walls 154 a and 154 b, and a second end-wall156 b at the other end of the side-walls 154 a and 154 b. The walls canbe configured in a rectilinear pattern or other suitable patterns toreceive the platen 170.

[0047] The platen 170 is positioned in the recess 152 of the sub-platen150. The platen 170 can be a plate having a first side-face 172 a, asecond side-face 172 b opposite the first side-face 172 a, a firstend-face 174 a between one end of the side-faces 172 a and 172 b, and asecond end-face 174 b between the other end of the side-faces 172 a and172 b. In the embodiment shown in FIG. 3, the first side-face 172 a isadjacent to the first side-wall 154 a, the second side-face 172 b isadjacent to the second side-wall 154 b, the first end-face 174 a isadjacent to the first end-wall 156 a, and the second end-face 174 b isadjacent to the second end-wall 156 b. The platen 170 also includes abearing surface 176 facing the backside of the polishing pad 140 tosupport at least a portion of the polishing pad 140 in a planarizingzone under the head 132. The platen 170 further includes a back surface178 facing the base surface 153 of the sub-platen 150. The polishing pad140 is coupled to the bearing surface 176 during planarization so thatthe pad transmits lateral forces to the platen 170. Suitable devices andmethods for coupling the polishing pad 140 to the bearing surface 176are disclosed in U.S. patent application Ser. Nos. 09/285,319 filed onApr. 2, 1999, and 09/181,578 filed on Oct. 28, 1998, both of which areherein incorporated by reference.

[0048] The platen 170 can move with respect to the sub-platen 150 in alateral motion at least generally parallel to a planarizing plane P-P(FIG. 8). In this embodiment, the endpointing apparatus also includes abearing mechanism 180 (FIG. 8) to reduce the friction between the basesurface 153 of the sub-platen 150 and the back surface 178 of the platen170. The bearing assembly 180 can be a roller mechanism having aplurality of rollers attached to either the sub-platen 150 or the platen170 to allow the platen 170 to freely roll across the sub-platen 150.The bearing assembly 180 can also be a low-friction coating or lubricantbetween the base surface 153 and the back surface 178, or a flexiblebladder (not shown) between the sub-platen 150 and the platen 170. Instill another embodiment, the bearing assembly 180 can be a frictionlessdevice having a number of air bearings defined by air holes through thesub-platen 150 that are connected to a pressurized air source thatprovides a continuous layer of air between the sub-platen 150 and theplaten 170. In still another embodiment, the bearing assembly 180 can bea magnetic device including magnetic bearings that prevent the backsurface 178 from contacting the base surface 153 by positioning magneticfields of a like polarity adjacent to one another. In operation, thebearing assembly 180 can frictionally isolate the platen 170 from thesub-platen 150 so that the drag forces between the substrate assembly 12and the pad 140 drive the platen 170 laterally with respect to thesub-platen 150 without substantial friction losses.

[0049] The force detectors 190 (identified by reference numbers 190a-190 d) can be positioned between the walls of the recess 152 in thesub-platen 150 and the faces of the platen 170. Each force detector 190can be a contact sensor that contacts both the sub-platen 150 and theplaten 170 to sense the lateral forces exerted by the platen 170 againstthe sub-platen 150 in correlation to the lateral forces exerted by thesubstrate assembly 12 against the polishing pad 140 duringplanarization. Suitable contact force detectors are strain gauges,piezoelectric elements or other transducers that generate signalscorresponding to the force exerted by the platen 170 against thesub-platen 150. The force detectors 190 can be other sensors thatgenerate electrical signals corresponding to the lateral forces ordisplacement between the sub-platen 150 and the platen 170. For example,in other embodiments in which the force detectors 190 do not contact theplaten 170 and the sub-platen 150 does not have dead stops so that theplaten 170 can move relative to the sub-platen 150, the force detectors190 can be lasers, accelerometers, capacitance displacement sensors,linear variable differential transformers or other displacement sensors.

[0050] In the particular embodiment of the planarizing machine 100illustrated in FIGS. 7 and 8, four force detectors 190 a-190 d areconfigured along two orthogonal lateral axes L₁ and L₂. Each lateralaxis L₁ and L₂ defines a lateral axis along which the drag forcesbetween the pad 140 and the substrate assembly 12 can be measured togenerate the drag force waveform 432 shown in FIG. 5. In otherembodiments, the planarizing machine 100 can have only one forcedetector positioned along one axis, or two force detectors positionedalong two orthogonal axes, or any number of force detectors positionedbetween the walls of the sub-platen 150 and the faces of the platen 170.For example, in an embodiment having two force detectors 190 positionedalong orthogonal axes, a first force detector 190 a can contact thefirst end-wall 156 a and the first end-face 174 a at a first forcedetector site, a second force detector 190 b can contact the firstside-wall 154 a and the first side-face 172 a at a second force detectorsite, and dead stops can be substituted for the force detectors 190 cand 190 d. The first end-wall 156 a and the first side-wall 154 a of thesub-platen 150 accordingly define first and second stop surfaces, andthe first end-face 174 a and the first side-face 172 a of the platen 170accordingly define first and second contact surfaces. In still anotherembodiment, the first and second force detectors 190 a and 190 b can bepositioned as explained above, and the dead stops or force detectors 190c and 190 d can be eliminated by sizing the platen 170 such that thesecond end-face 174 b abuts the second end-wall 156 b and the secondside-face 172 b abuts the second side-wall 154 b.

[0051]FIG. 9 is a schematic cross-sectional view of the planarizingmachine 100 in accordance with another embodiment of the invention. Inthis embodiment, the sub-platen 150 has a post 155 projecting upwardlyfrom the base surface 153, and the platen 170 is fixedly attached to thepost 155. The walls 172/174 of the platen 170 do not contact either deadstops, the faces 154/156 of the sub-platen 150, or other devices thatinhibit the platen 170 from moving with respect to the sub-platen 150.The movement of the substrate assembly 12 across the polishing pad 140accordingly displaces the platen 170 relative to the sub-platen 150 andgenerates torsional forces in the post 155 that are expected to beproportionate to the drag force between the substrate assembly 12 andthe polishing pad 140. The force detector 190 can be a strain gaugeattached to the post 155 to measure the torsional displacement of thepost 155, a laser, or another type of displacement sensor. The forcedetector 190 accordingly senses the change in the displacement or thetorsional forces exerted on the platen 170 and sends a correspondingsignal to the processor 199 a.

[0052]FIG. 10 is a schematic cross-sectional view of the planarizingmachine 100 in accordance with another embodiment of the invention inwhich a number of small posts 155 attach the platen 170 to thesub-platen 150. As with the embodiment of the planarizing machine shownin FIG. 10, the walls 172/174 of the platen 170 do not contact eitherdead stops, the faces 154/156 of the sub-platen 150, or other devicesthat inhibit the platen 170 from moving with respect to the sub-platen150. The posts 155 can be threaded studs having a diameter ofapproximately 1.0 inch and a length of 3.0 inches made from metal, highdensity polymers or other suitable materials. The posts 155 can also beother supports that can flex more in one direction than others, and theposts 155 can be made from other materials. The posts 155 of thisembodiment accordingly do not frictionally isolate the platen 170 fromthe sub-platen 150, but rather they deflect to control the motionbetween the platen 170 and the sub-platen 150 in correspondence to thedrag forces between the substrate assembly 12 and the polishing pad 140.The force detectors 190 accordingly measure the displacement between theplaten 170 and the sub-platen 150 to determine the drag forces betweenthe substrate assembly 12 and the polishing pad 140.

[0053]FIG. 11 is a schematic isometric view of a planarizing machine 100in accordance with still another embodiment of the invention. In thisembodiment, the planarizing machine 100 has a circular platen 170 andthe recess 152 in the sub-platen 150 has a single circular wall 154. Theplaten 170 accordingly has a single, circular side-face 174. The platen170 can be coupled to the sub-platen 150 by any of the bearings 180 orposts 155 described above with reference to FIGS. 7-10.

[0054]FIG. 12 is a schematic isometric view of a planarizing machine 200in accordance with another embodiment of the invention, and FIG. 13 is aschematic cross-sectional view of the planarizing machine 200 shown inFIG. 12 taken along line 13-13. The planarizing machine 200 has asub-platen 250 coupled to a rotary drive mechanism 251 to rotate thesub-platen 250 (arrow R), a platen 270 movably coupled to the sub-platen250, and a polishing pad 240 attached to the platen 270. The sub-platen250 has a base surface 253 facing the polishing pad 240 and a tab 254projecting upwardly from the base surface 253. The tab 254 has a stopsurface 256 facing in the direction of the rotation of the sub-platen250. The platen 270 includes an opening 271 having a contact surface 272facing the stop surface 256 of the tab 254. The planarizing machine 200further includes a bearing assembly 280 that can be the same as thebearing assembly 180 described above with reference to FIG. 8. Theplanarizing machine 200 also includes a force detector 290 contactingthe stop surface 256 of the tab 254 and the contact surface 272 of theplaten 270.

[0055] The planarizing machine 200 is expected to enhance the accuracyof detecting the endpoint of planarizing a substrate assembly in rotaryplanarizing applications. In operation, a carrier assembly 230 (FIG. 13)moves a carrier head 232 to press the substrate assembly 12 against aplanarizing surface 242 of the polishing pad 240. The rotary driveassembly 251 also rotates the sub-platen 250 causing the tab 254 topress the force detector 290 against the contact surface 272. Thesub-platen 250 accordingly rotates the platen 270 in the direction R,but the drag force between the substrate assembly 12 and the polishingpad 240 resists rotation in the direction R. The bearing assembly 280allows the drag forces between the substrate assembly 12 and theplanarizing surface 242 to drive the contact surface 272 of the platen270 against the force detector 290 in correlation to the drag forces. Asthe drag force increases between the substrate assembly 12 and theplanarizing surface 242, the force detector 290 accordingly detects anincrease in the lateral force that the platen 270 exerts against the tab254. The force detector 290 is coupled to a processor 299 to convert thesignals from the force detector 290 into data that can be analyzed todetermine the endpoint of the planarizing process as described abovewith reference to FIGS. 2-6.

[0056]FIG. 14 is a schematic cross-sectional view of a carrier system330 for a planarizing machine in accordance with another embodiment ofthe invention. The carrier assembly 330 can include a carrier head 332having a lower portion 333 with a lower cavity 334 to receive asubstrate assembly 12 and an upper portion 336 with an upper cavity 338.A pivoting joint 350 is attached to the head 332 in the cavity 338, anda drive-shaft 339 is pivotally attached to the joint 350. In thisembodiment, the endpointing apparatus includes a primary support memberdefined by the head 332, a secondary support member defined by thedrive-shaft 339, and a first contact surface defined by the side-wall ofthe upper cavity 338. In one embodiment, the joint 350 is a gimbal jointor other bearing assembly that allows universal pivoting between thehead 332 and the shaft 339. The carrier head 332 also includes a forcedetector 390 attached to an interior wall of the cavity 338. The forcedetector 390, for example, can be an annular piezoelectric ring.

[0057] In operation, the drag forces between the substrate assembly 12and the polishing pad 140 cause the shaft 339 to pivot about the joint350 such that the lower end of the shaft 339 contacts the force detector390. The force exerted by the driveshaft 339 against the force detector390 will be proportional to the drag forces between the substrateassembly 12 and the polishing pad 140. Accordingly, the isolated dragforce parameter of this embodiment is the displacement between the shaft339 and the carrier head 332. The force detector 390 is coupled to aprocessor 199 a (FIG. 2) to detect the endpoint of the planarizingprocess in a manner similar to that described above with respect toFIGS. 2-6.

[0058] D. Monitoring and Controlling Applications

[0059] The planarizing machines and methods described above withreference to FIGS. 2-14 are expected to enhance the accuracy ofendpointing CMP processing compared to processes and devices thatmonitor changes in the current of the drive motors. The methodsdescribed above with reference to FIGS. 2-6, for example, accuratelyendpoint CMP processing because they accurately estimate the exposuretime of the endpoint layer by measuring the peak drag forces between thesubstrate assembly and the polishing pad along a lateral axis to obtaina peak drag force waveform, developing a peak drag force curve from thepeak drag force waveform, and determining a reference time at theintersection of a first line corresponding to a downwardly slopingsection of the drag force curve and a second line corresponding to arelatively flat section of the drag force curve. One aspect of severalembodiments of methods set forth above with respect to FIGS. 2-6 is thatthe drag force monitoring systems accurately measure the minimum andmaximum peak drag forces along a lateral axis generally parallel to aplane defined by the pad/substrate interface. Another aspect of severalembodiments of these methods is that the peak drag forces, or thedifferences between the maximum peak drag forces and the minimum peakdrag forces, can be correlated with time in a peak drag force curve thataccurately indicates an estimated exposure time for the endpoint layer.Compared to conventional endpointing methods that may or may not providea significant signal change as the endpoint layer is exposed, thepeak-to-peak processing of the drag force waveform provides a moresignificant change to identify the exposure of the endpoint layer. Assuch, several embodiments of the methods described above with referenceto FIGS. 2-6 can accurately endpoint CMP processing.

[0060] The planarizing machines described above with reference to FIGS.2 and 7-14 are further expected to enhance the accuracy of endpointingCMP processing because they isolate a drag force parameter that is notinfluenced by energy losses unrelated to the drag force at thepad/substrate interface. In contrast to conventional planarizingprocesses that endpoint CMP processing using the current of the drivemotors, several embodiments of the planarizing machines described abovewith reference to FIGS. 7-14 measure the drag force between thesubstrate assembly and the polishing pad by isolating the displacementor the lateral forces between either a platen and sub-platen, or acarrier head and a drive shaft. The isolated drag force parameterprovides a much more accurate indication of the actual drag force at thepad/substrate interface than measuring motor current because energylosses and other factors associated with moving the carrier head or thepolishing pad do not influence or otherwise overshadow the changes indrag force between the pad and the substrate assembly. The endpointingapparatuses and monitoring systems described above with reference toFIGS. 7-14, therefore, are expected to enhance the accuracy of detectingthe endpoint in CMP processing.

[0061] From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A method for diagnosing mechanical or chemical-mechanicalplanarization processing of microelectronic-device substrate assemblies,comprising: sensing peak drag forces between a microelectronic substrateassembly and a polishing pad along a first lateral axis; processing thesensed peak drag forces to generate a force-time relationship betweenthe peak drag forces and time; and estimating the status of a parameterof the planarizing process by analyzing changes in the force-timerelationship.
 2. The method of claim 1 wherein: the substrate assemblycomprises a shallow-trench-isolation structure including a substratehaving trenches, an endpoint layer over the substrate, and a cover layerover the endpoint layer that fills the trenches; and estimating thestatus of a parameter of the planarizing process comprises assessing anendpoint at the endpoint layer by performing a first regression on adownward slope in the force-time relationship to determine a first line,performing a second regression on a relatively flat slope in theforce-time relationship to determine a second line, assessing areference time at an intersection of the first and second lines, andterminating removal of material from the substrate assembly at anendpoint time equal to the reference time plus a predeterminedover-polish time.
 3. The method of claim 1 wherein: the substrateassembly comprises a shallow-trench-isolation structure including asubstrate having trenches, an silicon nitride endpoint layer over thesubstrate, and a silicon dioxide cover layer over the endpoint layerthat fills the trenches; and estimating the status of a parameter of theplanarizing process comprises assessing an endpoint at the endpointlayer by performing a first regression on a downward slope in theforce-time relationship to determine a first line, performing a secondregression on a relatively flat slope in the force-time relationship todetermine a second line, assessing an exposure time at an intersectionof the first and second lines, and terminating removal of material fromthe substrate assembly at an endpoint time equal to the exposure timeplus a predetermined over-polish time.
 4. The method of claim 1 whereinestimating the status of a parameter of the planarizing processcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from a decreasing slope in the force-timerelationship to an increasing slope.
 5. The method of claim 1 whereinestimating the status of a parameter of the planarizing processcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from an increasing slope in the force-timerelationship to a decreasing slope.
 6. The method of claim 1 whereinestimating the status of a parameter of the planarizing processcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from a decreasing slope in the force-timerelationship to a relatively flat slope.
 7. The method of claim 1wherein estimating the status of a parameter of the planarizing processcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from an increasing slope in the force-timerelationship to a relatively flat slope.
 8. The method of claim 1wherein: the substrate assembly includes a substrate, an endpoint layerover the substrate and a cover layer over the endpoint layer; andestimating the status of a parameter of the planarizing processcomprises assessing exposure of the endpoint layer by monitoring achange from a decreasing slope of the force-time relationship to anincreasing slope.
 9. The method of claim 1 wherein: the substrateassembly includes a substrate, an endpoint layer over the substrate anda cover layer over the endpoint layer; and estimating the status of aparameter of the planarizing process comprises assessing exposure of theendpoint layer by monitoring a change from an increasing slope of theforce-time relationship to a decreasing slope.
 10. The method of claim 1wherein: the substrate assembly includes a substrate, an endpoint layerover the substrate and a cover layer over the endpoint layer; andestimating the status of a parameter of the planarizing processcomprises assessing exposure of the endpoint layer by monitoring achange from a decreasing slope of the force-time relationship to arelatively flat slope.
 11. The method of claim 1 wherein: the substrateassembly includes a substrate, an endpoint layer over the substrate anda cover layer over the endpoint layer; and estimating the status of aparameter of the planarizing process comprises assessing exposure of theendpoint layer by monitoring a change from an increasing slope of theforce-time relationship to a relatively flat slope.
 12. The method ofclaim 1 wherein: the substrate assembly includes a substrate, anendpoint layer over the substrate and a cover layer over the endpointlayer; and estimating the status of a parameter of the planarizingprocess comprises assessing exposure of the endpoint layer by monitoringa change from a relatively flat slope of the force-time relationship toa decreasing slope.
 13. The method of claim 1 wherein: the substrateassembly includes a substrate, an endpoint layer over the substrate anda cover layer over the endpoint layer; and estimating the status of aparameter of the planarizing process comprises assessing exposure of theendpoint layer by monitoring a change from a relatively flat slope ofthe force-time relationship to an increasing slope.
 14. A method ofmechanical or chemical-mechanical planarization of microelectronicsubstrate assemblies, comprising: measuring lateral displacement orlateral forces between a first component coupled to one of the substrateassembly or the polishing pad and a second component in either a carrierassembly holding the substrate assembly or a table supporting thepolishing pad, the lateral displacement or lateral forces between thefirst and second components being proportionate to lateral drag forcesbetween the substrate assembly and the polishing pad; processing themeasured lateral displacement or lateral forces between the first andsecond components to generate a force-time relationship between thelateral drag forces and time; and estimating the status of a parameterof the planarizing process by analyzing changes in the force-timerelationship.
 15. The method of claim 14 wherein: the substrate assemblycomprises a shallow-trench-isolation structure including a substratehaving trenches, an endpoint layer over the substrate, and a cover layerover the endpoint layer that fills the trenches; and estimating thestatus of a parameter of the planarizing process comprises assessing anendpoint at the endpoint layer by performing a first regression on adownward slope in the force-time relationship to determine a first line,performing a second regression on a relatively flat slope in theforce-time relationship to determine a second line, assessing areference time at an intersection of the first and second lines, andterminating removal of material from the substrate assembly at anendpoint time equal to the reference time plus a predeterminedover-polish time.
 16. The method of claim 14 wherein: the substrateassembly comprises a shallow-trench-isolation structure including asubstrate having trenches, an silicon nitride endpoint layer over thesubstrate, and a silicon dioxide cover layer over the endpoint layerthat fills the trenches; and estimating the status of a parameter of theplanarizing process comprises assessing an endpoint at the endpointlayer by performing a first regression on a downward slope in theforce-time relationship to determine a first line, performing a secondregression on a relatively flat slope in the force-time relationship todetermine a second line, assessing an exposure time at an intersectionof the first and second lines, and terminating removal of material fromthe substrate assembly at an endpoint time equal to the exposure timeplus a predetermined over-polish time.
 17. The method of claim 1 whereinestimating the status of a parameter of the planarizing processcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from a decreasing slope in the force-timerelationship to an increasing slope.
 18. The method of claim 1 whereinestimating the status of a parameter of the planarizing processcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from an increasing slope in the force-timerelationship to a decreasing slope.
 19. The method of claim 1 wherein:the substrate assembly includes a substrate, an endpoint layer over thesubstrate and a cover layer over the endpoint layer; and estimating thestatus of a parameter of the planarizing process comprises assessingexposure of the endpoint layer by monitoring a change from a decreasingslope of the force-time relationship to a relatively flat slope.
 20. Themethod of claim 1 wherein: the substrate assembly includes a substrate,an endpoint layer over the substrate and a cover layer over the endpointlayer; and estimating the status of a parameter of the planarizingprocess comprises assessing exposure of the endpoint layer by monitoringa change from an increasing slope of the force-time relationship to arelatively flat slope.
 21. A method of mechanical or chemical-mechanicalplanarization of microelectronic substrate assemblies, comprising:removing material from a substrate assembly using a polishing pad bypressing the substrate assembly against the polishing pad at apad/substrate interface and moving at least one of the substrateassembly and the pad relative to the other in a planarizing plane;generating a drag force-waveform by sensing drag forces between thesubstrate assembly and the polishing pad along a single lateral axisgenerally parallel with the planarizing plane; creating a force-timerelationship by correlating peak amplitudes of the sensed drag forceswith time; and terminating planarization of the substrate assembly at anestimated endpoint time defined by a time relative to a change in themeasured peak amplitudes of the waveform.
 22. The method of claim 21wherein: the substrate assembly comprises a shallow-trench-isolationstructure including a substrate having trenches, an endpoint layer overthe substrate, and a cover layer over the endpoint layer that fills thetrenches; and terminating planarization comprises determining theestimated endpoint time by performing a first regression on a downwardslope in the force-time relationship to determine a first line,performing a second regression on a relatively flat slope in theforce-time relationship to determine a second line, assessing areference time at an intersection of the first and second lines, andadding a predetermined over-polish time to the reference time.
 23. Themethod of claim 21 wherein: the substrate assembly comprises ashallow-trench-isolation structure including a substrate havingtrenches, an silicon nitride endpoint layer over the substrate, and asilicon dioxide cover layer over the endpoint layer that fills thetrenches; and terminating planarization comprises determining theestimated endpoint time by performing a first regression on a downwardslope in the force-time relationship to determine a first line,performing a second regression on a relatively flat slope in theforce-time relationship to determine a second line, assessing anexposure time at an intersection of the first and second lines, andadding a predetermined over-polish time to the exposure time.
 24. Themethod of claim 21 wherein terminating planarization comprises assessingan onset of planarity of the substrate assembly by monitoring a changefrom a decreasing slope in the force-time relationship to an increasingslope.
 25. The method of claim 21 wherein terminating planarizationcomprises assessing an onset of planarity of the substrate assembly bymonitoring a change from an increasing slope in the force-timerelationship to a decreasing slope.
 26. The method of claim 21 wherein:the substrate assembly includes a substrate, an endpoint layer over thesubstrate and a cover layer over the endpoint layer; and terminatingplanarization comprises assessing exposure of the endpoint layer bymonitoring a change from a decreasing slope of the force-timerelationship to a relatively flat slope.
 27. The method of claim 21wherein: the substrate assembly includes a substrate, an endpoint layerover the substrate and a cover layer over the endpoint layer; andterminating planarization comprises assessing exposure of the endpointlayer by monitoring a change from an increasing slope of the force-timerelationship to a relatively flat slope.
 28. A method of mechanical orchemical-mechanical planarization of microelectronic substrateassemblies, comprising: removing material from a substrate assemblyusing a polishing pad by pressing the substrate assembly against thepolishing pad and moving at least one of the substrate assembly and thepad relative to the other in a planarizing plane; measuring lateraldisplacement or lateral forces between a first component coupled to oneof the substrate assembly or the polishing pad and a second component ineither a carrier assembly holding the substrate assembly or a tablesupporting the polishing pad, the lateral displacement or lateral forcesbetween the first and second components being proportionate to lateraldrag forces between the substrate assembly and the polishing pad;processing the measured lateral displacement or lateral forces betweenthe first and second components to generate a force-time relationshipbetween the lateral drag forces and time; and estimating an endpointtime of the substrate assembly using a change in the force-timerelationship.
 29. The method of claim 28 wherein: the substrate assemblycomprises a shallow-trench-isolation structure including a substratehaving trenches, an endpoint layer over the substrate, and a cover layerover the endpoint layer that fills the trenches; and estimating theendpoint time of the substrate assembly comprises performing a firstregression on a downward slope in the force-time relationship todetermine a first line, performing a second regression on a relativelyflat slope in the force-time relationship to determine a second line,assessing an exposure time at an intersection of the first and secondlines, and adding a predetermined over-polish time to the exposure time.30. The method of claim 28 wherein: the substrate assembly comprises ashallow-trench-isolation structure including a substrate havingtrenches, an silicon nitride endpoint layer over the substrate, and asilicon dioxide cover layer over the endpoint layer that fills thetrenches; and estimating the endpoint time of the substrate assemblycomprises performing a first regression on a downward slope in theforce-time relationship to determine a first line, performing a secondregression on a relatively flat slope in the force-time relationship todetermine a second line, assessing an exposure time at an intersectionof the first and second lines, and adding a predetermined over-polishtime to the exposure time.
 31. The method of claim 28 wherein estimatingthe endpoint time comprises assessing an onset of planarity of thesubstrate assembly by monitoring a change from a decreasing slope in theforce-time relationship to an increasing slope.
 32. The method of claim28 wherein estimating the endpoint time comprises assessing an onset ofplanarity of the substrate assembly by monitoring a change from anincreasing slope in the force-time relationship to a decreasing slope.33. The method of claim 28 wherein: the substrate assembly includes asubstrate, an endpoint layer over the substrate and a cover layer overthe endpoint layer; and estimating the endpoint time comprises assessingexposure of the endpoint layer by monitoring a change from a decreasingslope of the force-time relationship to a relatively flat slope.
 34. Themethod of claim 28 wherein: the substrate assembly includes a substrate,an endpoint layer over the substrate and a cover layer over the endpointlayer; and estimating the endpoint time comprises assessing exposure ofthe endpoint layer by monitoring a change from an increasing slope ofthe force-time relationship to a relatively flat slope.
 35. A method ofmechanical or chemical-mechanical planarization of microelectronicsubstrate assemblies, comprising: removing material from a substrateassembly using a polishing pad by pressing the substrate assemblyagainst the polishing pad and moving at least one of the substrateassembly and the pad relative to the other in a planarizing plane;generating a drag force waveform by sensing drag forces between themicroelectronic substrate assembly and the polishing pad along at leasta first lateral axis extending generally parallel to the planarizingplane; processing the waveform to plot peak amplitudes of the waveformover time, the plot having a first section and a second section;performing a first regression on the first section to define a firstline and a second regression on the second section to define a secondline; determining an intersection time corresponding to an intersectionbetween the first and second lines; estimating an endpoint time of thesubstrate assembly by adding a predetermined over-polish time to theintersection time; and terminating removal of material from thesubstrate assembly at the estimated endpoint time.
 36. The method ofclaim 34 wherein: the substrate assembly comprises ashallow-trench-isolation structure including a substrate havingtrenches, an silicon nitride endpoint layer over the substrate, and asilicon dioxide cover layer over the endpoint layer that fills thetrenches; and determining the intersection time comprises performing thefirst regression on a downward slope of the first section in theforce-time relationship to determine the first line, performing thesecond regression on a relatively flat slope of the second section inthe force-time relationship to determine the second line, and locatingthe intersection of the first and second lines to identify when thesilicon nitride endpoint layer is exposed.
 37. A method of mechanical orchemical-mechanical planarization of microelectronic substrateassemblies, comprising: providing a substrate assembly having asubstrate, an endpoint layer having lands at a desired endpointelevation in the substrate assembly, and a cover layer over the endpointlayer; removing material from the cover layer of the substrate assemblyusing a polishing pad by pressing the substrate assembly against thepolishing pad and moving at least one of the substrate assembly and thepad relative to the other in a planarizing plane; measuring lateraldisplacement or lateral forces between a first component coupled to oneof the substrate assembly or the polishing pad and a second component ineither a carrier assembly holding the substrate assembly or a tablesupporting the polishing pad, the lateral displacement or lateral forcesbetween the first and second components being proportionate to lateraldrag forces between the substrate assembly and the polishing pad;processing the measured lateral displacement or lateral forces betweenthe first and second components to generate a force-time relationshipbetween the lateral drag forces and time; and performing a firstregression on a downwardly sloping section of the force-timerelationship to define a first line and a second regression on arelative flat section of the force-time relationship occurring after thedownwardly sloping section to define a second line; determining anexposure time of the endpoint layer by assessing an intersection betweenthe first and second lines; estimating an endpoint time of the substrateassembly by adding a predetermined over-polish time to the exposuretime; and terminating removal of material from the substrate assembly atthe estimated endpoint time.
 38. The method of claim 37 wherein: thesubstrate assembly comprises a shallow-trench-isolation structureincluding a substrate having trenches, an silicon nitride endpoint layerover the substrate, and a silicon dioxide cover layer over the endpointlayer that fills the trenches; and determining the intersection timecomprises performing the first regression on a downward slope of thefirst section in the force-time relationship to determine the firstline, performing the second regression on a relatively flat slope of thesecond section in the force-time relationship to determine the secondline, and locating the intersection of the first and second lines toidentify when the silicon nitride endpoint layer is exposed.